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A&P I > Vision/Image - Cal > Flashcards

Vision/Image - Cal Flashcards

1
Q

Light is ___(bent, focused) as it progresses through refractive structures of the eye

A

refracted

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2
Q

A receptor ___ is produced when light strikes the retinal photoreceptors of the eye

A

potential

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3
Q

The neural layer of the retina processes visual data, then sends nerve impulses into axons that comprise the

A

optic nerve

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4
Q

Impulses are conveyed to the ___, and on to the cerebral cortex where they are interpreted as images

A

thalamus

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5
Q

Refraction (bending) of light occurs when light rays traveling through a transparent substance pass into a second transparent substance with a

A

different density .

This is because the light travels at different speeds in materials of different densities

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6
Q

A beam of light travels in a uniform front after being produced

When the beam travels toward a biconvex lens, One part of the beam arrives at the lens before the rest of the beam. Those light rays enter the lens first, and ___. But the remaining parts of the beam continue at the original, faster, speed until they, too, encounter the lens

A

slow down

The different arrival times, and consequent different times of slowing, cause the beam to refract (bend)

Slide 4-8

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7
Q

light converges, and is focused by the ___ lens

A

convex

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8
Q

concave lens causes the light to?

A

diverge

slide 8

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9
Q

Light rays entering the eye are refracted by the __ and ___

A

cornea and the lens

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10
Q

Most refraction occurs at the ___, with the lens providing much of the remainder.

A

cornea

The aqueous humor and vitreous body are minor participants in light refraction

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11
Q

Images formed on the retina are inverted.. meaning?

A

Upside down

Show left-to-right reversal

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12
Q

The brain learns early in life to coordinate visual images with the orientation of objects, so the inverted images are not a problem

A

Cool

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13
Q

Light rays reflected from objects ___than about 20 feet from the viewer are essentially parallel

A

further

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14
Q

At this range (>20 ft) the ciliary muscle is reasonably ____, and the lens is fairly flat

A

relaxed

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15
Q

Light rays reflected from objects closer than about 20 feet from the viewer are?

A

not parallel

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16
Q

At ranges closer than 20 ft, The lens must be ___ to properly focus the image

A

thicker

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17
Q

In accommodation, The ciliary muscle ___, reducing tension on the suspensory ligaments, and allowing the lens to assume a more spherical shape

A

contracts

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18
Q

The increase in the curvature of the lens for near vision is called?

A

Accomodation

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19
Q

Absent tension on the lens via the suspensory ligaments (zonular fibers), the lens assumes a ___ shape

A

convex

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20
Q

When the ciliary muscle is relaxed, the ___ acts like a spring pulling on the lens through the suspensory ligaments, causing the lens to become less convex.

A

choroid

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21
Q

When the ciliary muscle contracts, it stretches the choroid, releasing the tension on the lens and the lens becomes ____

A

thicker

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22
Q

the minimum distance from the eye that an object can be clearly focused with maximum accommodation

A

Near point of vision

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23
Q

The lens loses elasticity with aging, and therefore also loses its ability to accommodate. The loss of elasticity of the lens with age, and the accompanying results, is called

A

presbyopia

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24
Q

begins in the mid-forties: people who have not previously needed glasses begin to need them, and those who already wear glasses need bifocals

A

Presbyopia

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25
Q

The normal eye is termed

A

emmetropic

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26
Q

It refracts light rays from an object ___ away, such that a clear image is formed on the retina

A

20 feet (6 meters)

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27
Q

Refraction abnormalities prevent emmetropic eyesight from always being the case, as in . . .

A

Myopia (nearsightedness)

Hyperopia
(farsightedness)

Astigmatism (irregular curvature of the cornea)

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28
Q

Myopia

Hyperopia

Astigmatism

A

nearsightedness

farsightedness

irregular curvature of the cornea

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29
Q

occurs when the eyeball is too long relative to the focusing power of the cornea and lens

A

myopia

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30
Q

The image is focused in front of the retina

A

myopia

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31
Q

The condition may be due to an elongated eyeball or thickened lens

Correction is by use of a concave lens

A

myopia

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32
Q

occurs when the eyeball is too short relative to the focusing power of the cornea and lens

A

hyperopia

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33
Q

The image would be focused behind the retina

A

hyperopia

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34
Q

The condition may be due to a shortened eyeball or thin lens

Correction is by use of a convex lens

A

hyperopia

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35
Q

due to an irregular curvature of either the cornea or the lens

A

Astigmatism

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36
Q

The result is that parts of the image are blurred or distorted, and out of focus

A

Astigmatism

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37
Q

Correction is by use of a lens that rotates the axis of the light going into the eye

A

Astigmatism

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38
Q

When the pupil is ___, light rays that are allowed to enter the eye through the small opening are more parallel than when the opening is large

A

small

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39
Q

Part of the overall accommodation mechanism is ___ of the circular muscles of the iris to constrict the pupil, which occurs simultaneously with changes in the thickness of the lens

A

contraction

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40
Q

Many animals see one set of objects out of one eye, and another set of objects out the other eye
In humans, both eyes focus on only one set of objects, resulting in

A

binocular vision.

Binocular vision provides depth perception, and three-dimensional perspective

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41
Q

results when light rays from an object strike corresponding points on the two retinas, but each eye sees the same image from slightly different angles

A

Binocular vision

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42
Q

The brain fuses the two slightly different images delivered by each eye, providing (literally “seeing solid”)?

A

stereoscopic vision

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43
Q

As we move closer to an object the eyes must rotate ___ in order for the light rays from the object to strike the same point on both retinas

A

medially

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44
Q

the medial movement of the two eyeballs so that both are directed toward the object being viewed

A

Convergence

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45
Q

The outer segments of rods are

Those of cones are

A

cylindrical, or rod-shaped

tapered, or cone-shaped

The names rod and cone were assigned during the 1830’s based on the shape of the cells when viewed in the microscope

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46
Q

The two types of photoreceptors are not evenly distributed in the retina

A

Rods and cones

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47
Q

most highly concentrated in the central fovea (identified as “cone peak”), and dramatically decrease in density moving away from the fovea

A

Cones

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48
Q

Cones are most highly concentrated in the

A

central fovea

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49
Q

Rods are most highly concentrated in a ring around the

A

foveal pit.

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50
Q

Although there are no rods in the ___, where rods are present in the retina they are generally more densely concentrated than cones

A

fovea

51
Q

The optic disc (blind spot) is?

A

receptor free

52
Q

The outer segment is the end of the photoreceptor next to the

A

pigmented layer

53
Q

It is in the ____ that light energy is transduced into a receptor potential

A

outer segment

54
Q

The ____ of rods and cones are layered to increase the surface area available for trapping light

A

outer segments

55
Q

The___ of each cone consists of folds, similar to a long pleated fabric

A

outer segment

56
Q

The tip of the outer segment of each rod contains a stack of ___ piled up like coins in a wrapper, near the base the membrane is folded like it is in cones

A

discs

57
Q

Outer segments of both rods and cones are easily destroyed by light, and are sloughed off at the tip, then the fragments are phagocytized by

A

pigment epithelial cells

58
Q

Phagocytic activity occurs in a ___ rhythm. Rod tips are phagocytized in the morning after first exposure to light. Cone phagocytosis is triggered by darkness, and occurs at night.

A

circadian.

Turnover of outer segments is fairly rapid

59
Q

The inner segment contains:

A

Cell nucleus
Golgi apparatus
Mitochondria (many)

60
Q

The ____ end of both rods and cones expands into a synaptic terminal containing numerous synaptic vesicles

A

proximal

61
Q

colored, integral proteins in the plasma membrane of the outer segment of rods and cones

A

Photopigments

62
Q

Photopigments undergo structural changes when they

A

absorb light

63
Q

Photopigments associated with vision contain two parts:

A

Retinal, a derivative of vitamin A formed from carotene

Opsin, which is a glycoprotein

64
Q

a derivative of vitamin A formed from carotene

A

Retinal

65
Q

a glycoprotein

not very specific I know…

A

Opsin

66
Q

The photopigment in rods is?

…which absorbs blue to green light most effectively

A

rhodopsin

67
Q

retinal + opsin =

A

rhodopsin

68
Q

There are three different cone photopigments, one in each of three types of cone, each having a different absorption maximum:

A

Photopsin I, 2, 3

69
Q

Photopsin I

Photopsin II

Photopsin III

A

(yellowish absorption maximum)

(green absorption maximum)

(blue-violet absorption maximum)

70
Q

More specifically, it is the ___ portion of the photopigment which is different in each of the different photopigments

A

opsin

71
Q

Retinal is the same in all photopigments, and it is retinal which is the key in transducing light energy into

A

electrical signals

72
Q

In darkness, retinal has a bent shape called

A

cis-retinal.

73
Q

Opsin and retinal fit together nicely when retinal is

A

cis-retinal

74
Q

When cis-retinal absorbs a photon of light, it straightens out to a shape called

A

trans-retinal

75
Q

The cis to trans conversion is called

A

isomerization

76
Q

In the straight, ___ form, opsin and retinal no longer fit, and they dissociate

A

trans-retinal

77
Q

This dissociation sets up a series of events in the photoreceptor that eventuates in perception of the?

(ie., in seeing)

A

photon

78
Q

After light-induced isomerization of retinal from cis to trans form, the ___ rapidly decomposes during the next few milliseconds

A

rhodopsin

Obviously, the photopigments must be reconstituted or vision would cease

79
Q

That reconstitution of photopigments is termed

A

regeneration

80
Q

Rhodopsin has a “normal” ___ color

A

reddish

81
Q

In the presence of light cis-retinal is converted to trans-retinal, and the opsin, now minus the detached retinal, becomes

A

colorless

Slide 36 (sounds weird I know)

This is termed bleaching of photopigment

82
Q

An enzyme called ____converts trans-retinal back to cis-retinal

A

retinal isomerase

83
Q

The ___ can now rebind to the opsin, reforming a functional photopigment

A

cis-retinal

This is called regeneration

84
Q

Photopigment bleaching, and ___ occur in the eyes

A

regeneration

85
Q

When one is in the light, photopigment is bleached. At the same time, other molecules are being

A

regenerated

86
Q

Regeneration is too slow in daylight to keep up with bleaching in the rods, so __ contribute little to daylight vision

A

rods

87
Q

___ photopigments do regenerate rapidly enough that some cis form is always present

A

Cone

88
Q

Dark adaptation occurs when photopigments are able to regenerate in the dark without being bleached by light. It takes about 30 to 40 minutes for bleached ___ to fully regenerate, which is the amount of time it takes to become dark adapted

A

rhodopsin

89
Q

Adaptation to sudden light takes only a ___ as the visual system adjusts to the brighter environment by decreasing sensitivity

A

few seconds

90
Q

The momentary dazzling that is experienced when one moves from darkness into bright light is caused by the strong stimulation of both ____ and the large amounts of photopigments that are broken down almost instantaneously, thereby producing a flood of signals

A

rods and cones,

91
Q

an inability to distinguish between certain colors, and results from the absence or a deficiency of one of the three cone photopigments

A

Color blindness

92
Q

The most common OF color bliness type is ___ color blindness, in which a photopigment sensitive to red light or to green light is missing
It is generally an inherited trait.

A

red-green

93
Q

Slide 42

A

What do you see

94
Q

this is an inability to see well at low light levels

A

nyctalopia

95
Q

Typically caused by prolonged vitamin A deficiency and the consequent below normal amount of rhodopsin, and which can also result in rod degeneration

A

nyctalopia

Vitamin A supplements will restore function if they are administered before degenerative changes occur

96
Q

The retina processes visual signals at synapses among the various types of retinal neurons. Some visual inputs are enhanced, and others are

A

discarded

97
Q

Pathways of processing may be converging or diverging, but ____ is the general rule since there are hundreds more photoreceptors than ganglion cells

A

convergence

98
Q

Many rods (6 to 600) synapse with a single ___, but a given bipolar will generally synapse with only one cone

A

bipolar cell

99
Q

The convergence of many rods into a single bipolar cell increases light sensitivity of rod vision, but decreases the ___ of the image

A

acuity

100
Q

Cone vision is less ___, but has a higher acuity

A

sensitive

101
Q

Horizontal cells and ___ cells attenuate the differences between parts of the retina that are strongly stimulated and parts that are less stimulated, as well as assist in the differentiation of colors

A

amacrine

102
Q

Slide 48, 49

A

low res

103
Q

Axons of the ____ cells provide output from the retina to the brain. They exit the eyeball as the ____

A

retinal ganglion

optic nerve

104
Q

Axons of the optic nerve pass through the ____, where some cross to the opposite side, and some do not cross

A

optic chiasm

105
Q

Upon passing through the optic chiasm the axons are now considered to comprise the ___.

A

optic tract

106
Q

After optic tract, they enter the brain and terminate in the ____ of the thalamus

A

lateral geniculate nucleus

107
Q

There (in lateral geniculate nucleus ) they synapse with neurons having axons that form the optic radiations, which project to the primary visual area in the ____ of the cerebral cortex

A

occipital lobes

108
Q

The ____ of an eye is everything that can be seen by that eye

A

The visual field

109
Q

Due to the placement of our eyes, the two visual fields overlap, which is the field of

A

binocular vision

110
Q

The visual field of each eye is divided into two regions:

A

Nasal (central) half

Temporal (peripheral) half

111
Q

For each eye, light rays from an object in the nasal half of the visual field fall on the ___ half of the retina, and light from an object in the temporal half of the visual field fall on the ___ half of the retina

A

temporal

nasal

112
Q

Further, due to the pattern of crossing over or not crossing over at the optic chiasma, visual information from the right half of each visual field is conveyed to the___side of the brain

A

left

(and visual information from the left half of each visual field is conveyed to the right side of the brain)

Slide 54, 55

113
Q

This is because the axons from the temporal half of each retina (do or don’t) cross, but continue directly to the lateral geniculate nucleus of the thalamus on the same side

A

DO NOT

Temportal half doesn’t cross

Slide 56

114
Q

For each eye, light rays from an object in the nasal half of the visual field fall on the temporal half of the retina, and light from an object in the temporal half of the visual field falls on the ___ half of the retina.

A

nasal

DUPLICATE SLIDE 57

115
Q

Further, due to the pattern of crossing over or not crossing over at the optic chiasma, visual information from the right half of each visual field is conveyed to the left side of the brain, and visual information from the left half of each visual field is conveyed to the __ side of the brain . This is because the axons from the temporal half of each retina do not cross, but continue directly to the lateral geniculate nucleus of the thalamus on the same side

A

right

DUPLICATE SLIDE 57

116
Q

Axon collaterals of retinal ganglion cells project to the ___ where they are involved in circuits that govern constriction of the pupils and coordination of head and eye movements

A

midbrain

117
Q

Collaterals also go to the ___ of the hypothalamus which establishes circadian rhythms based in part on impulses of light perception from the eyes

A

suprachiasmatic nucleus

118
Q

Optic radiations are the projection of axons from the ___ to the primary visual area of the cortex on the same side

A

thalamus

119
Q

Loss of vision in an otherwise normal eye

A

Amblyopia

120
Q

caused by either no transmission or poor transmission of visual stimulation through the optic nerve to the brain during early childhood or for a sustained period thereafter due to strabismus (cross-eyes, or eye misalignment), anisometropia (one eye significantly near/far sighted) cataract, trauma, etc

A

Amblyopia

121
Q

Detection in early childhood increases the chance of successful treatment (20/20 eye chart screening is insufficient)

A

Amblyopia

122
Q

Sometimes called “wandering eye” or “lazy eye” but the term is inaccurate since there is no “laziness” of the eye. “Lazy brain” would be a more accurate term. The term “lazy eye” is further imprecise because “lazy eye” is also used for strabismus

A

Amblyopia

123
Q

A number of different and separate systems (probably at least three) within the cerebral cortex operate to process and interpret visual signals:

A

One system process information related to the shape of objects

One system processes information about the color of objects

Another system processes information about movement, location, and spatial organization

124
Q

A number of different and separate systems (probably at least three) within the cerebral cortex operate to process and interpret visual signals:

A

shape of objects

color of objects

movement, location, and spatial organization

A&P I (21 decks)

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